The overall aim of this study is to determine how gallbladder function is influenced by the neurons that lie within the wall of the gallbladder. This aim is clinically relevant since about 15% of the US population suffers from disease of the biliary system, and about 600,000 cholecystectomies are performed in the USA each year. Furthermore, disruption of the nerves that supply the gall bladder reportedly causes malfunction of the gall bladder in man and in experimental animals. The first aim of this proposal is to evaluate, with electrophysiolOgical and histochemical approaches, how neurons in the wall of the gallbladder respond to inputs that they receive in healthy and in diseased states. The inputs that will be studied include the following: 1) input from the vagus nerve; 2) local release of neuropeptides from sensory (possibly pain) fibers; 3) projections from neurons in the myenteric plexus of the duodenum; and 4) immune-mediated compounds such as histamine and prostaglandins, that are released by inflammatory cells during cholecystitis. The second aim is to use intracellular and patch clamp recording techniques to evaluate the electrophysiological properties of gallbladder smooth muscle cells, and to study how these cells respond to neurotransmitters that are known to be produced by gall bladder neurons. The third aim of this proposal is to use human gallbladders obtained from cholecystectomies to determine the structural, neurochemical, and physiological properties of the nerves and nerve cells that lie in the wall of the human gallbladder. Experiments are proposed to evaluate how human gallbladder neurons respond to cholecystokinin and prostaglandin E2. Cholecystokinin is a hormone that is known to cause gallbladder emptying following meals; in animals it has been shown to act, at least in part, through a neural mechanism. Prostaglandin E2 is known to be present at high levels in inflamed gall bladders, and it is thought to act through a neural mechanism to cause gallbladder contractions. Data from the experiments described in this proposal will elucidate the means by which neurons in the wall of the gallbladder respond to incoming cues, and how these neurons, in turn, influence the smooth muscle tone of the organ.